Fibrillation process

ABSTRACT

There is provided a commercial process for fibrillating a fibrillatable tape at windup speeds in excess of 500 feet per minute. In this process the tape is subjected to the action of at least four fluid twisting means wherein the direction of twist imparted to the tape is completely and sharply reversed between adjacent twisting means and the tape is advanced from one fluid twisting means to another while being maintained under a tension of from about 0.05 to about 0.2 grams per denier.

United States Patent 1191 Gibbon 1451 Jan. 2, 1973 s41 FIBRILLATIONPROCESS 3,303,169 2 1967 Pitzl ..57/34 x Inventor: John D. Gibbon 7000Thermal 3,395,525 8/1968 Eddy ..57/3l X Charlotte, NC 23211 FOREIGNPATENTS OR APPLICATIONS Filedr l 9, 1970 6,912,566 2/1970 Netherlands..57 34 B [21] Appl' 70;"3 Primary Examiner-Werner H. Schroeder Remed sApplication Data Attorney-Thomas J. Morgan, S. D. Murphy and H. J.

Greenwald [63] Continuation-in-part of Ser. No. 59,383, July 30,

57 ABSTRACT 52 U.S. c1. ..s7/1s7 F, 57/773 is Pwvided a cmmerial Processfor fibrillating 51 1111.01. ..D02g 1/16 a fibrillatab'e winduP speedsin excess [58] Field of Search 57/34 R 34 B 773 774 feet per minute. Inthis process the tape is subjected to 57/157 28/1 72112 the action of atleast four fluid twisting means wherein the direction of twist impartedto the tape is completely and sharply reversed between adjacent twisting[56] References cued means and the tape is advanced from one fluidtwist- UNITED STATES PATENTS ing means to another while being maintainedunder a tension of from about 0.05 to about 0.2 grams per de- 3,116,588l/l964 Brecn et a1. ..57/157 i 3,125,793 3/1964 Gonsalves ..57/34 B X3,214,899 11/1965 Winninger, Jr. et a1. ..57/157 X 5 Claims, 3 DrawingFigures PA'ITENTEDJANZ ms 3,707,837

l6 l8 7 7 J FIG,2 FIG.3

- INVENTOR JOHN D. GIBBON ATTORNEY FIBRILLATION PROCESS This is acontinuation in part of application Ser. N 0. 59,383 which is entitledFibrillated Film Yarn and which was filed on July 30, 1970.

Fibrillation processes, wherein filamentary articles are produced fromlongitudinally oriented fibrillatable synthetic polymeric tapes orfilms, are well known to the art. These processes, however, suffer fromthe disadvantage that they generally can only be operated at relativelylow throughput speeds and filament yarn cannot be produced via thenwhich can compete in price with filament yarn produced by conventionalprocesses. The throughput speeds used in these processes are generallyabout 300 feet per minute, and the maximum throughput speed which can beused in these processes is about 500 feet per minute. Throughput speedis often referred to as windup speed and is the speed at which thefibrillated yarn is taken through the last fibrillating means and/orwound up.

It is thus an object of this invention to provide a fibrillation processwhich can be operated at throughput speeds greater than 500 feet perminute and which produces a fibrillated yarn with good uniformity. Inaccordance with this invention, there is provided a process forfibrillating them fibrillatable tape at a throughput speed greater than500 feet per minute comprising the step of subjecting a travelingfibrillatable tape under a tensionof from about 0.05 toabout 0.2 gramsper denier to the action of at least four fluid twisting means whereinthe direction of twist imparted to the tape is completely reversedbetween adjacent twisting means.

In the aforementionedprocess it is preferred to work at throughputspeeds in excess of 1000 feet per minute. A surprising advantage of thisprocess is that the fibrillated yarn produced thereby has very gooduniformity even when very high throughput speeds are used.

' This process is applicable to any fibrillatable tape, i.e. any tapeshowing a readiness to split in the lateral direction (a tape whereinthe bonds in the lateral direction are weak when compared to the bondsin the longitudinal direction). Various fibrillatable tapes aredisclosed, e.g., in U. S. Pat. Nos. 2,185,789; 3,214,899; 3,242,035;3,323,978; andthe like.

In this process the fibrillatable tape is subjected to the action of atleast four fluid twisting means so that the direction of twist impartedto the tape is completely reversed between adjacent twisting means andthere is substantially no change in the longitudinal direction ofmovement of the tape between successive twisting means.

FIG. 1 is a schematic view of the dual twisting means.

FIG. 2 is a cross-section of one fluid twistingelement freely, and twistis imparted to the strand by a vortex of whirling fluid which rotatesabout the axis of travel of the strand in direct contact therewith) workwell in applicants invention. Thus, e.g., the apparatus shown in FIGS.1, 2, and 3 may be used in applicants invention. This apparatus iscomprised of two co-operating opposite rotating twisting means.Apparatus 10 is comprised of a U-shaped member with co-axial bores 12and 14 through the legs of the U and slots 16 and 18 which communicatewith bores 12 and 14 respectively. Fluid is supplied to manifold box 20by connector 22 (which is supplied with a pressurized fluid such as,e.g. water or air), and this fluid then passes through fluid passageways24 and 26 into bores 12 and 14 respectively. Said fluid passageways areessentially tangential to bores 12 and 14 with axes in planesperpendicular to the axis of bores 12 and 14, respectively. They arethus positioned with respect to bores 12 and 14 so as to producerespectively therein fluid vortices rotating in opposite directions.

In apparatus 10, because the axes of fluid passageways 24 and 26 lie ina plane perpendicular to the axes of bores 12 and 14, the vorticesgenerated at the intersections of said passageways 24 and 26 with bores12 and 14 respectively are propagated equally along the axes of bores 12and 14 from the points of vortex generation. In another usefulembodiment a preferential direction and intensity of vortex propagationmay be obtained 'by placing the axes of fluid passageways 24 and 26 inplanes intersecting the axes of bores 12 and 14 at angles which areother than p'erpendicular. In these embodiments the twisting of thevortices not only fibrillate the tape but also tension the tape in apreferred direction. It is preferred that the planes in which the fluidpassageways lie make an angle of from 15 to to the axis of the bores. Itis more preferred that this angle be from 30 to 60 and most preferredthat this angle be from 45 to 60.

In applicants process it is preferred that the perimeter of the tape inthe yarn passageway be from about 4 to about 12 millimeters, theperimeter of the yarn passageway (which, in the apparatus describedabove, would be bores 12 and 14) be from about 5 to about 20millimeters, the perimeter of the air passageway (which would bepassageways 24 and 26 in the apparatus described above) be from about1.25 to about 10 millimeters, and the ratio of the tape perimeter/yampassageway perimeter be from about 0.1 to 1.5 (and most preferably fromabout 0.3 to about 0.7). If the yarn passageway and air passageway arecylindrical, it is preferred that the ratio of the yarn passagewaydiameter/air passageway diameter be from about 0.1 to about 0.7 (andmost preferably from about 0.2 to about 0.5).

Any series of at least four fluid twisting means wherein the directionof twist imparted to the tape is completely reversed between adjacenttwisting means and there is substantially no change in the longitudinaldirection of movement of the tape between successive twisting means willwork well in this process. The fluid used in said twisting means may bevirtually any gas which approaches ideal gas behavior and does not reactwith the tape to be fibrillated. Thus, e.g., air, steam, nitrogen,oxygen, carbon dioxide, etc., may be used in the process of thisinvention; because itis one of the cheapest gases, it is preferred touse air as said fluid. In said twisting means the fluid velocity shouldreach from about 0.5 to about 1.0 sonic velocity at the point of contactwith the strand.

The direction of twist imparted to the tape is reversed between adjacenttwisting means. Thus, e.g., if the fibrillatable tape is passed throughthe apparatus shown in FIG. 1, it will have a clockwise twist impartedto it in bore 12 and counter-clockwise twist imparted to it in bore 14;the tape may then be subjected to a third fluid twisting means whereinclockwise twist is imparted to it and a fourth twisting means whereincounter-clockwise twist is imparted to it.

It is preferred, for reasons of economy and efficiency, to have a pairof twisting means embodied in the same apparatus. Such apparatus areillustrated, e.g., in FIGS. 1, 2 and 3.

In each apparatus which is comprised of a pair of twisting means it ispreferred that the adjacent twisting means he no further than about 3inches apart so that the direction of twist will be sharply reversed,and it is most preferred that said adjacent twisting means be no furtherthan about one inch apart. The distance between each apparatus which iscomprised of two twisting means may be as great as is practical; thus,e.g., two such apparatus may be from about 6 to about 1000 inches apart.It is preferred that the two adjacent apparatus, each of which arecomprised of two adjacent twisting means, be from about 12 to about 500inches apart, and it is more preferred that they be from about 15 toabout 72 inches apart. In the most preferred embodiment, they are about24 inches apart.

As the fibrillatable tape is being subjected to the action of at leastfour fluid twisting means, it should be maintained under a tension offrom about 0.05 to about 0.2 grams per denier to insure goodfibrillation of the tape, although it is preferred to maintain it at atension of from about 0.05 to about 0.15 grams per denier, and it ismost preferred to maintain it at a tension of about 0.1 grams perdenier. The tape may be maintained at the prescribed tension by godetrolls or winding apparatus pulling the tape through the fluid twistingmeans. Alternatively, if the passageways of the twisting means are at anangle of from about I to about 89 with respect to the axis of thepassageway through which the tape travels, the tape may be maintainedunder the prescribed tension by the action of the fluid twisting means.

In the preferred embodiment air supplied to the fluid twisting meanswill be under a pressure of from about 10 to about 250 p.s.i.g.,although it is preferred that said pressure be from about to about 100p.s.i.g. and it is most preferred that said pressure be from about 40 toabout 80 p.s.i.g. When said preferred pressure and the fluid twistingmeans shown in FIG. 3 are used in the process of this invention, apoly(ethylene terephthalate) tape, e.g., will have a twist of greaterthan 20,000 turns/minute imparted to it.

Via this process from about 5 to about 300 fibrils per tape will beproduced, although it is preferred to adjust the operating conditions ofthis invention so that from about 25 to about 200 fibrils per tape willbe produced.

This process is applicable to any fibrillatable tape such as, e.g.,fibrillatable tape essentially comprised of poly (ethyleneterephthalate), poly(trimethylene terephthalate), poly(tetramethyleneterephthalate), polypropylene, nylon, etc. Inasmuch as a fibrillatedfilm yarn produced from tape essentially comprised of poly(ethyleneterephthalate) has the desirable properties of poly(ethyleneterephthalate) yarn (such as high modulus, susceptibility to texturing,etc.) and is cheaper and has better aesthetic characteristics than yarncurrently available, it is preferred to apply this process to producefibrillated yarn comprised of poly( ethylene terephthalate).

Another process that the applicant has discovered (which may be usedtogether with applicants fluid twisting means process but can also beused with any fibrillating means), affords an especially advantageousmeans of fibrillating poly (ethylene terephthalate). It is verydifficult to draw and fibrillate poly(ethylene terephthalate) inaccordance with the procedure the art disclosed for polypropylenefibrillation, for when this is done a weak, non-uniform, commerciallyuseless yarn is usually produced. The following process solves thisproblem.

In this latter process a tape essentially comprised of polyester withspecified properties is fibrillated. The spun tape is from about 0.0002to about 0.005 inches thick. The thickness of the tape may be controlledby extruding a film and slitting a tape to the required dimensions or byextruding a tape and controlling the dimensions of the die through whichit is extruded and/or the quench height (the distance from the die faceto the quenching medium). It is preferred to extrude the tape through aslit die which measures about 1 inch by from about 0.003 to about 0.015inches and to have a quench height of from about 0.2 to about 2 inches,and it is most preferred to extrude the tape through a slit diemeasuring about 1 inch X about 0.0006 inch and to use a quench height ofabout 0.5 inches. Any quenching medium can be used. The preferredquenching medium is water, and when it is used the quench temperature(i.e., the temperature of the quench medium) is about 0 to about 60centigrade, although it is preferred that it be about 30 centigrade. Onemay, alternatively, quench on chill rollers, e.g.. The aforementionedparameters may be varied to obtain the desired tape thickness of fromabout 0.0002 to about 0.005 inches; any of the infinite combination ofvariables by which one obtains the aforementioned tape thickness iswithin the scope of applicants discovery.

After said polyester tape is extruded and quenched, it may be dried to amoisture content of less than about 2 percent (by weight of tape),although when this step is employed it is preferred to dry the tape to amoisture content of less than about 1 percent. Drying should be used ifa hot air drawing step is employed.

The tape used in this latter process may or may not be comprised of fromabout 0.1 to about 25 percent (by weight of polyester) of incompatiblepolymer. If incompatible polymer is used in said latter process, it mustbe non reactive and be dispersed finely in the polyester so that theaverage particle size of the dispersed incompatible polymer is less thanabout 8 microns. Polymer selected from the group consisting ofpolyethylene and polypropylene is the preferred incompatible polymer,although other polymers, which can be extruded with polyester withoutundergoing serious degradation of themselves which adversely affect(e.g. degrade) the polyester, may be used (elg.

nylon 6,nylon 6.6, polystyrene, etc.). i

The most preferred incompatible polymer is polypropylene, and it ispreferred to use at least about 0.5 weight percent of it and incorporateit into the tape. It is more preferred to use from about 1 to about 4percent of polypropylene, and it is most preferred to use about 2 to 3percent of polypropylene.

The mere addition of polypropylene in the latter process will not, inand of itself, promote fibrillation: the polypropylene should be finelydispersed throughout the poly (ethylene terephthalate) so that theaverage size of the polypropylene particles therein is less than about 8microns, although it is preferred that they be less than about 4microns, and best results are obtained when they are less than about 1micron. Many methods well known to the art may be used to obtain therequired degree of dispersion.

One method applicant has used to obtain the required degree ofdispersion is to mix poly(ethylene terephthalate) and polypropylene andextrude the mixture at a high temperature (e.g., about 285 centigrade)through a slit die. It is believed that, for this method to work well,the viscosities of the poly(ethylene terephthalate) and thepolypropylene should be about equal. Polypropylene is relativelynon-newtonian, i.e., its viscosity is dependent upon shear rate, whereaspoly (ethylene terephthalate) is nearly newtonian; thus it is believedthat, with the use of the proper conditions, at some stage during theextrusion process the apparent viscosities of the two polymers will bematched. It is believed that, in order to get good dispersion with thismethod, the following conditions should exist; (1) the poly(ethyleneterephthalate) should have an intrinsic viscosity of from about 0.45 toabout 0.75, although it is preferred that it has an intrinsic viscosityof from about 0.61 to about 0.67; (2) the polypropylene should have amelt flow index (as measured by ASTM D-1238 62T, condition B orconditionL) of from about 8 to about 22, although it is preferred thatit have a melt flow index of about (3) a mixture comprised of from about0.5 to about 5 percent of polypropylene (by weight of poly[ ethyleneterephthalate1) and poly(ethylene terephthalate) should be prepared; (4)this mixture should be extruded via a pack which imposes a shear forceof from about 60 to about 150 sec for from about 1 to about 2 seconds;and (5) the extrusion temperature should be from about 280 to about 300centigrade, it being preferred to use an extrusion temperature of about285 centigrade. Under these conditions good dispersion of polypropyleneresults. It is to be understood that this is merely one means ofobtaining the desired degree of dispersion, and any polyester tapecomprised of the desired amount of polypropylene with the desired degreeof dispersion as well as the process of using said tape to producefibrillated polyester yarn are within the scope of this invention.

This latter process, which utilizes the polyester tape describedhereinabove, can make yarn with denier of from about 30 to about 10,000;this yarn is useful for knitting, weaving, and tufting.

The polyester tape which applicant has discovered should, prior to thetime it is fibrillated, be subjected to a step which applicant has foundto be important for good fibrillation: it is hot drawn to a draw ratioof from about 3.3 to about 4.2 while being subjected to a temperature offrom about to about 140 centigrade, and thereafter it is subjected to atemperature of from about to about 230 centigrade for from about 0.01 toabout 0.2 seconds. It is preferred that the polyester tape be hot drawnto a draw ratio of about 3 .5 while it is being subjected to atemperature of from about 80- to about centigrade for from about 0.08 toabout 0.8 seconds and that is thereafter be subjected to a temperatureof from about 200 to about 230 centigrade for from about 0.02 to about0.1 seconds preferably by passing it over a hot plate or a hot air oven,the use of the hot plate being most preferred. The residence time, theperiod of time during which said tape is being hot drawn and subjectedto a temperature of from about 80 to about 140 centigrade, is a functionof, e.g., the speed at which the process is being run; it generally isfrom about 0.1 to about 1 second, and it most preferably is from about0.2 to about 0.4 seconds.

The polyester tape may be drawn in hot air at a preferred hot airdrawing temperature of from about 80 to about centigrade, it being morepreferred to use a hot air drawing temperature of about 80 centigrade;hot air drawing is the preferred drawing method. Alternatively thepolyester tape may be drawn in hot water at a preferred hot waterdrawing temperature of from about 80 to 100 centigrade, it being morepreferred to use a hot water drawing temperature of about 90 centigrade.The temperatures described hereinabove are the temperatures of the tapeand not those of the drawing medium.

It is preferred that said polyester tape, after it has been subjected tothe aforementioned step of hot drawing it and thereafter subjecting itto a temperature of from about 120 to about 230 centigrade, have beendrawn to a total draw ratio of from about 4 to about 5.5. Although thetape may be drawn to a draw ratio of from about 5.5 in one stage, it ispreferred that it be so drawn in two stages. In the first stage, whichcorresponds to the first part of the aforementioned step, the tape maybe drawn to a draw ratio of from about 3.3 to about 4.2 while beingsubjected to a temperature of from about 80 to about 120 centigrade forfrom about 0.1 to about 1 second. In the second stage, which correspondsto the second part of the aforementioned step, the tape may be furtherdrawn to increase the total draw ratio to from about 4 to about 5.5while being subjected to a temperature of from about 120 to about 230centigrade for from about 0.02 to about 0.2 seconds.

The drawn tape can be fibrillated by any of the processes well known tothe art which will provide sufficient stress to fibrillate it. Thus,e.g., the tape may be fibrillated as taught in British Pat. No.l,ll8,9l2 by contacting it with a roller having on its periphery aplurality of grooves of equal pitch and cutting edges of equal pitchdisposed substantially in spiral form. Thus, e.g., the tape may befibrillated as taught in U. S. Pat. No. 3,302,50l by passing it over astationary brush or a similar shredding means or, alternatively, bypiercing the film through its thickness in a plurality of points withoutshredding the film by, e.g., moving the piercing means longitudinally orlaterally through the film as it is pierced. Thus, e.g., the tape may befibrillated as taught in U. S. Pat. No. 3,177,557 by passing it througha zone of high turbulence provided by a high velocity jet of stream ofair or other gas.

lt is preferred to fibrillate said poly(ethylene terephthalate) tape bythe "four fluid twisting means process of this invention wherein thetape is subjected to the action of at least four fluid twisting meanswherein the direction of twist imparted to the tape is completely andsharply reversed between adjacent twisting means and the tape isadvanced from one fluid twisting means to another while being maintainedunder a tension of from about 0.05 to about 0.2 grams per denier.

As was stated hereinabove, the latter process of this invention may beadvantageously used to fibrillate any fibrillatable tape. Thus, e.g., itmay be used to fibrillate poly(tetramethylene terephthalate).Poly(tetramethylene terephthalate) tape can be prepared in substantialaccordance with the procedure described for the preparation ofpoly(ethylene terephthalate) tape. The addition of at least 0.5 percentof polypropylene (by weight) is not essential to produce goodfibrillation with poly(tetramethylene terephthalate) tape, but said useof polypropylene is advantageous in three respects; it makes theextruded poly(tetramethylene terephthalate) film more stable and easierto process, it renders said film slightly easier to fibrillate, and thefibrillated yarn produced from said film is stronger than yarn producedfrom poly(tetramethylene terephthalate) film which is not comprised ofpolypropylene. Said.poly(tetramethylene terephthalate), with or withouta minor amount of polypropylene, is extruded into a film or tape whichis uniaxially drawn to a draw ratio of from about 4.0 to from about 6.0,although it is preferred to use a draw ratio of about 5.0. The drawnfilm is then slit into the required denier, which is generally fromabout 150 to about 600, and fibrillated in accordance with the processof this invention.

In a typical process which may be used for the production of e.g.,fibrillated poly(ethylene terephthalate) yam, poly (ethyleneterephthalate) polymer and the required amount of polypropylene ispassed through an extruder, and through a tape die into a water quench(alternatively, a chill roll may be used). Then it is wound on a godet,passed through a hot air oven, wound over a second godet, passed over ahot plate, passed over a third godet, and subjected to the action offour fluid false twisting means in apparatus. Thereafter the fibrillatedyarn is wound by tension controlled winders. Said typical process isonly one of the many which may utilize applicants invention.

This process enables one to produce a continuous filament fibrillatedyarn with unique properties. This yarn is comprised of random-lengthfibrils of a synthetic organic high polymer wherein: the averagewidth/thickness ratio of cross sections of the fibrils (the aspectratio) is from about 2/1 to about 12/1, and the aspect ratios of thecross sections of the fibrils range from about 0.5/l to about 20/1; thefibrils in the yarn exceeding 40 centimeters in length comprise at lease70 percent (by weight) of the yarn; the tenacity of the yarn is fromabout 0.1 to about grams per denier; the total denier of the yarn isfrom about 30 to about 10,000, and the average denier per fibril of thefibrils comprising the yarn is from about 0.5 to about 60; theelongation of the yarn is from about 0.5 to about percent; and theinitial modulus of the yarn is from about 2 to about 300.

This yarn has many unique advantages. For any given polymer, this yarnhas a higher tenacity (particularly at pearance); this characteristic isparticularly obvious (and advantageous) when the yarn is used as acarpet face yarn. Fabrics produced from this yarn have a uniquedesirable luster and excellent printability. The cover effect of thefibrillated polyester yarns of this invention is greater than the covereffect of the same denier round cross section filament yarn produced byconventional processes. Most importantly, this yarn is substantiallycheaper to make than regular filament yarn.

The fibrillated yarn of this invention is comprised of random-lengthfibrils of a crystalline synthetic organic high polymer, i.e., anypolymer capable of possessing an appreciable amount of crystallinitywhich will retain orientation on relaxation after stretching. Thus,e.g., polymers such as polyethylene; polypropylene; polybutene;polymethyl-B-butene; polystyrene; polyamides such as polyhexamethyleneadipamide, poly (ethylene sebacamide), poly(methylenebis-p-cyclohexyleneadipamide), and polycaprolactam; acrylics such aspolymethylmethacrylate and methyl methacrylate; polyethers such as polyoxymethylene; halogenated polymers such as polyvinyl chloride,polyvinylidene chloride, tetrafluoroethylene, hexafiuoropropylene, andthe like; polyurethanes; cellulose esters of acetic acid, propionicacid, butyric acid, and the like; polycarbonates; polyacetals;polyesters of the formula (wherein n is from 2 to about 10 andpreferably is 2, 3, or 4); and the like, can be used to prepare the yarnof this invention. Other materials such as delustrants, incompatiblepolymers, etc., may comprise the yarns of this invention. Thus the yarnsof this invention are essentially comprised of the polymers described,i.e., at least percent by weight) of the yarn consists of one or more ofsaid polymers.

The fibrillated yarn of applicants invention is virtuallyindistinguishable in appearance from a continuous filament yarn. This islargely due to the fact that the average width/thickness ratio (theaspect ratio") of cross sections of the fibrils comprising applicantsnovel yarn is from about 2/1 to about 12/1, and the aspect ratios of thecross sections of the fibrils range from about 0.5/ l to about 20/ l.The preferred yarn of applicants invention is essentially comprised ofpoly(ethylene terephthalate) yarn, and the average aspect ratio of thefibrils of this yarn is from about 3/1 to about 5/ 1, the aspect ratiosof the cross sections of the fibrils ranging from about 2.5/ 1 to about7/1.

The tenacity of the fibrillated yarns of applicants invention arerelatively high, ranging from about 0.1 to up to about 10 grams perdenier (as determined by a ment, poly(ethylene terephthalate)fibrillated yarn, has

a tenacity of from about 0.5 to about 7 grams per deni- There are manylong fibrils in the yarns of applicant's invention. The fibrilsexceeding 40 centimeters comprise at least 70 percent (by weight) ofthese yarns.

The fibrillated yarns of this invention have a denier of from about 30to about 10,000, and the average denier per fibril of the fibrilcomprising the yarn is from about 0.5 to about 60. The elongation ofthese yarns is from about 0.5 to about 75 percent, and the initialmodulus of these yarns is from about 2 to about 300.

Applicants novel fibrillated yarns do not need to be twisted as do someof theweb-like yarns described in the prior art.

The preferred yarns of applicants invention contain less than four freefibril ends per centimeter and thus generally are not as hairy as arethe fibrillated products of the prior art; this property contributes tothe continuous yarn-like appearance of the yarns of this invention. Afree fibril end is a fibril which is unattached on one end, protrudesfrom the yarn bundles, and is visible to the naked eye.

The polymer from which the yarns of this invention are made should havea sufficiently high molecular weight so that the polymer is fiberforming.

In order to better describe some of the preferred embodiments ofapplicants invention, the below mentioned examples are presented. Unlessotherwise mentioned, all parts are by weight and all temperatures are indegrees centigrade.

In examples 1-4, a tape of the polymer under investigation was preparedby extrusion and drawing under conditions which gave favorablefibrillation at about 1000 feet per minute windup speed with the processof this invention (four fluid twisting means). This tape was thenfibrillated over a range of speeds from 150 feet per minute up to 2000feet per minute in processes wherein it was subjected to only two fluidtwisting means and to four fluid twisting means. A sample for eachrunwwas cross-sectioned (five cross-sections for each sample atapproximately 3 meter intervals),'and the number of fils was counted.The average of the 5 cross-sections was then taken as the degree offibrillation for a sample.

In analyzing the results, the speed at which one need run the twotwisting means" process with the four twisting means process wascompared. The results were averaged to reduce the degree of uncertaintyproduced by the statistical variability of the fibril count. In all runsthe twisting means used was essentially the same as that disclosed inthe Figures, wherein the apparatus disclosed comprises two twistingmeans (and is referred to as a jet in these Examples). When, e.g., otherfluid twisting means are used, similar results are obtained.

EXAMPLE 1 Poly(ethylene terephthalate) with an intrinsic viscosity of0.61 and 2 percent (by weight of polyethylene terephthalate) ofpolypropylene with a melt flow index of were mixed and then subjected ina pack to a shear force of 120 sec for about 1 second and extruded via apack through a slit die (which was 1 X 0.0005 inch); the extrusiontemperature was 280 centigrade. The extruded tape was quenched in water(at a quench height of 1.25 inch) and spun. The spun tape was 10 mm wideand had a total spun denier of 3150. The spun tape was then drawn in afirst stage at a draw temperature of about 1 10 centigrade and a drawspeed of 175 feet per minute to a draw ratio of 3.5/1, and thereafter itwas drawn in a second stage at a draw temperature of about 200centigrade and a draw speed of 120 feet per minute to a draw ratio of1.4/1.

This tape was then fibrillated with one jet (comprising two fluidtwisting means wherein the direction of twist imparted to the tape iscompletely reversed between adjacent twisting means) and two' jets. Themaximum speeds one could use to get any given degree of fibrillationwith one jet and two jets operated at the same conditions are shownbelow.

Number of Maximum Speed One Maximum Speed One FiIs/T ape Can Use WithOne Can Use With Two Jet To Obtain The Jets To Obtain The SpecifiedDegree Specified Degree of Fibrillation of Fibrillation (Feet/Minute)(Feet/Minute) 60 0 (Le, at no 100 speed could the one jet give one thisdegree of fibrillation) 50 0 170 40 300 35 130 410 30 230 greater 600than 25 500 greater 600 than EXAMPLE 2 A poly(ethylene terephthalate)tape was prepared in substantial accordance with the procedure describedin Example 1, with the exception that the first stage draw ratio was3.6/1, the first stage take-up speed was 1080 feet per minute, the firststage draw temperature was 127 centigrade, the second stage draw ratiowas 1.3/1, and the second stage takeup speed was the same speed as thefibrillation speed. The tape was comprised of poly(ethyleneterephthalate) with an intrinsic viscosity of 0.61 and 2 percentpolypropylene with a melt flow index of 15.

This tape was then fibrillated with one jet and two jets. The resultsare presented below.

Number of Maximum Speed One Maximum Speed One Fils/T ape Can Use WithOne Can Use With Two Jet To Obtain The Jets To Obtain The SpecifiedDegree Specified Degree of Fibrillation of Fibrillation (Feet/Minute)(Feet/Minute 30 650 greater 2000 than This example differs from Example1 in that the tape was prepared at much higher drawing speeds; thiseffect increases the fibrillation for a given speed through the jets andat the higher speeds make the fibrillation less sensitive to changes inspeed.

llv

lt was observed that the use of the two jets decrease the number oflarge filaments, thus contributing to the uniformity of the yarn. Toquantify this observation the cross sections made for Example 2 wereexamined and the number of fils with a breadth to thickness ratiogreater than 6 were tabulated. On averaging, the following results wereobtained.

Wide Fil Count (Average) 1 jet 2 jets Temp. of 140 4.5 2.2 Speed effectaveraged Hot Plate, l70 2.2 "C 200 0.6 Speed 400 3.8 0.6 Temperatureeffects 800 4.0 1.6 average fpm 1200 3.8 2.0

1600 5.0 2.2 Overall average 3.7 L Temp and speed effects Total averagedThis experiment shows that the addition of the second jet is veryeffective in reducing the number of wide fils. Another effective methodof reducing wide fils is to increase the hot plate temperature to 200centigrade. With the use of two jets and a hot plate temperature of 200centigrade, the incidence of wide fils was almost eliminated.

EXAMPLE 3 ln substantial accordance with Example 1, a nylonfibrillatable tape comprised of 2 percent of polypropylene was prepared.The nylon 6.6 had a relative viscosity of 40, and the polypropylene hada melt flow index of 15. Total spun denier of the spun tape was 2000.

The term relative viscosity as employed in conjunction with the nylonpolymers may be defined as a measure of the ratio of the viscosity of asolution of a given strength of the polyamide in a given solvent to theviscosity of the solvent itself at the same prescribed temperature. Therelative viscosity values noted herein utilize 90 percent by weight ofaqueous formic acid as the solvent. The efflux time (t) of an 8.4percent by weight solution of the polyamide in the formic acid solventis determined and the ratio of said viscosity to the effiux time (t) ofthe solvent itself is the measure of relative viscosity as determined bythe equation:

The temperature employed for the determination of these viscosities is25 Centigrade.

The nylon tape was then fibrillated with one and two jets; the resultsare shown below.

Number of Maximum Speed Maximum Speed Fils/T ape (f.p.m., one jet)(f.p.m., two jets) 50 75 250 45 ISO 325 EXAMPLE 4 ln substantialaccordance with Example 1, a tape comprised of poly(tetramethyleneterephthalate) with an intrinsic viscosity of 0.80 and 2 weight percentof polypropylene (with a melt flow index of was prepared. The termintrinsic viscosity as used with reference to polyester polymers may bedefined as the limit of the ratio of solution viscosity to solventviscosity taken from one divided by the concentration of the polymer insolution as the concentration approaches zero (1; lirn co a units are indeciliters/gram. Measurements may be made of relative viscosity (on an 8percent solution polyester in orthochlorophenol) and converted tointrinsic viscosity by an empirical formula. The tape was 8 mm wide andhad a total spun denier of 4000. The draw ratio used was 5/1 and thedraw speed was 1500 feet per minute. The tape was fibrillated with onejet and two jets, and the results are shown below.

Number of Maximum Speed One Maximum Speed One Fils/Tape Can Use With OneCan Use With Two Jet To Obtain The Jets To Obtain The Specified DegreeSpecified Degree of Fibrillation of Fibrillation (Feet/Minute)(Feet/Minute) O 375 80 200 5 50 60 5 50 I200 5 8 625 l 500 56 700 2500EXAMPLE 5 In substantial accordance with Example 1, a tape 9 mm wide oftotal denier 3000 was extruded from a polymer mix of 2 percentpolypropylene (M. F. l. 15) and 98 percent poly(ethylene terephthalate)(0.61 intrinsic viscosity). This tape was drawn into hot air in twostages to a total draw ratio of 4.9/1. The drawn tape was .thenfibrillated by passing it through one of the jets disclosed in FIGS. 1,2a, and 2b at a rate of 50 feet per minute with an applied air pressureof 60 p.s.i.g. and a yarn tension of 75 grams. A fibrillated yarn withan average of 45 filaments was obtained. The yarn was then passedthrough another such jet at a rate of 200 feet per minute with anapplied air pressure of 60 p.s.i.g. and a yam tension of 50 grams. Theyarn obtained had an average of about 100 filaments per tape (asdetermined by a fibril count of microscopically prepared cross-sectionsof the yarn). The

length/breadth distribution of the yarn, estimated from thiscross-section, was as follows:

Length/Breadth Ratio Percent Frequency l-2 22 2-3 27 3-4 21 4-5 I 6 S-610 6-7 3 The average length/breadth ratio is 3.2. The yarn, has a totaldenier of 600 and an average denier per filament of about 6, has atenacity of 2.4 grams per denier, and an elongation of 12.5 percent.This yarn, as well as-the other yarns described herein, are useful inpolyester shaped articles; more particularly, said yarns are useful intextile fabrics and garments.

EXAMPLE 6 In substantial accordance with Example 5, an 800 denier drawntape was prepared and fibrillated through two of said jets at a rate of100 feet per minute with a yarn tension of 50 grams and an air pressureof 60 p.s.i.g. The yarn had an average of 68 filaments, with an averagelength/breadth ratio of 4.3.

EXAMPLE 7 In substantial accordance with Example 5, a poly(ethyleneterephthalate) tape was drawn uniaxially in two stages to a total drawratio of 4.9; the dimensions of the drawn tape were approximatelymicrons thick and 4.5 mm wide. The tape was subjected to the action oftwo of the aforementioned jets at a rate of 280 feet per minute with ayarn tension of 55 grams and an air pressure of 40 p.s.i.g. Theresulting fibrillated yarn had a tenacity of 2.45 grams per denier, anelongation of 4.7 percent, and an initial modulus of 84 grams perdenier. On average, about 51 filaments could be counted at across-section of the yarn. From microscopic examination thecross-section of an average filament could be described as essentiallyrectangular and had an average aspect ratio of 4.7/1. The total denierof the yarn was 684, with an average denier per filament of 13.4. Theyarn was very slightly hairy in appearance.

This yarn was four ply twisted into a thick yarn and tufted, as a faceyarn, into a carpet. Tufting performance was exceptionally good and,except for a pleasant sheen, performed similarly to continuous filamentcarpets from which it was difficult to distinguish. It was judged farsuperior to commercially available carpets of fibrillated polypropylene.

EXAMPLE 8 In substantial accordance with Example 7, a poly(ethyleneterephthalate) tape was drawn to a draw ratio of 5.4; the tape was 4.5mm wide and 16.5 microns thick. This tape was fibrillated by passing itthrough 3 of the aforementioned jets at a speed of 232 feet per minuteunder a yarn tension of 60 grams with an applied air pressure of 80p.s.i.g. A fibrillated yarn was obtained with a tenacity of 3.2 gramsper denier, an elongation of 4.5 percent, and initial modulus of 106grams per denier. The yarn had an average of 71 filam/ents per tape. Theaverage cross-section ratio was 3 l.

The continuous filament yarn was woven as filling yarn into a warp of 70denier polyester to give a fabric which would be suitable in upholsteryand drapery. After dyeing and heat setting, the fabric had a soft andpleasant handle and exhibited good drape and a pleasing and unusualsurface sparkle.

EXAMPLE 9 In substantial accordance with Example 5, a poly(ethyleneterephthalate) tape was prepared which had a denier of 680 and a filmthickness of 15 microns. This tape was fibrillated by passing it throughtwo of the aforementioned jets at 285 feet per minute under yarn tensionof 55 grams with air pressure of 40 p.s.i.g. being supplied to the jets.The tape fibrillated into a yarn composed of an average 51 filaments,corresponding to an average denier per filament of 13.4. The yarn hadonly 3 free ends per centimeter and a tenacity of 2.5 grams per denier..To produce fibrillation of this quality with only one jet (comprised ofonly two twisting means), it was necessary to lower the fibrillationspeed to feet per minute.

EXAMPLE 10 In substantial accordance with Example 5, a poly(ethyleneterephthalate) tape was prepared and fibrillated through two of saidjets at a speed of 532 feet per minute under a yarn tension of 60 gramsand with p.s.i.g. of air pressure being furnished the jets. The yarnproduced was 393 denier, had 48 filaments and a tenacity of 4.4 gramsper denier, was comprised of very EXAMPLE 11 Poly(tetramethyleneterephthalate) polymer with a relative viscosity of 37.5 was extruded ata temperature of 255 centigrade into a water quench to give a film 4.5mm wide with a denier of 1520. This tape was then drawn in hot air at atemperature in excess of 80 centigrade in two stages to a total drawratio of 5/1. The drawn tape was then fibrillated through two jetssimilar to those shown in FIGS. 1, 2a, and 2b at a speed of 50 feet perminute under a yarn tension of 50 grams with an applied air pressure of60 p.s.i.g. A fibrillated product was obtained with an average filamentcount of 34 and an average dpf of 8.9. The filament cross-section isrectangular with the thin dimension about 17 microns and the crosssection range between 1/1 and 4.5/l with about 70 percent of thefilaments being in the 2.5/1 to 3]] range. The yarn had an elongation of12.6 percent, a tenacity of 0.87 grams per denier, and an initialmodulus of 12.0 grams per denier at 60 percent strain rate.

EXAMPLE 12 Poly(tetramethylene terephthalate) polymer with a relativeviscosity of 37.5 was blended with 3 weight/percent of polypropylene(melt flow index 12) and extruded to give a film 7.5 mm wide with adenier of 4250 and a birefringence of 3.6.'The tape was drawn andfibrillated under the same conditions used in Example ll. A fibrillatedyarn was obtained with an average filament count of 26, average denierper filament of 33, and very few broken ends. The filament cross sectionwas rectangular with the thin dimension being 38 microns. The aspectratio range is from 2/1 to 7/1. The surface of the filament was verysmooth and in appearance very like similarly processed poly(ethyleneterephthalate) yarns. The yarn had a tenacity of 2.0 grams per denier,an elongation of 12 percent, and an initial modulus of 30 grams perdenier at 60 percent strain rate.

It is preferred that the yarns of this invention be comprised of atleast percent (by weight of yarn) of e.g., the preparation of carpetbacking materials. Furthermore, they can be used as tufting materialsfor artificial grass constructions.

terephthalate), poly(trimethylene The tapes described in this inventionhave utility for,

Although the above examples and descriptions of this invention have beenvery specifically illustrated, many other modifications will suggestthemselves to those skilled in the art upon a reading of thisdisclosure. These are intended to be comprehended within the scope ofthis invention.

What is claimed is: l. A process for fibrillating a fibrillatable tapeat a throughput speed of greater than 500 feet per minute comprising thesteps of:

a. subjecting a travelling fibrillatable tape to at least four fluidtwisting means;

b. tensioning said travelling fibrillatable tape so that it is under atension of from about 0.05 to about 0.2 grams per denier while beingsubjected to said fluid twisting means; and

c. contacting said tape with a vortex of whirling fluid in each of saidtwisting means, wherein said vortex 3 of whirling fluid rotates aroundthe axis of travel of the tape and the direction of rotation of thevortices is opposite in adjacent twisting means, whereby the directionof twist imparted to the tape is completely reversed between adjacenttwisting means.

crew gr The process of claim 1, wherein:

the first fluid twisting means said tape is subjected to is no furtherthan 3 inches away from the second fluid twisting means said tape issubjected to, and the third fluid twisting means said tape is subjectedto is no further than 3 inches away from the fourth fluid twisting meanssaid tape is subjected to; and said second and third fluid twistingmeans are from about 6 to about 1000 inches apart.

. The process of claim 2, wherein:

the fluid supplied to said twisting means is air,

. from about 10 to about 250 p.s.i.g. of air pressure are supplied toeach of said twisting means, whereby, the velocity of said air in saidtwisting means is from about 0.5 to about 1.0 sonic velocity, and

. said fibrillatable tape is comprised of at least percent (by weight)of poly(ethylene terephthalate) The process of claim 3, wherein: saidfibrillatable tape is maintained at a tension of from about 0.05 toabout 0.15 grams per denier;

. from about 20 to about p.s.i.g. of air pressure ar u lie to eac ofsaid twist'n means;

t? Hist uid twisting means is no further than about 1 inch away fromsaid second fluid twisting means, and said third fluid twisting means isno further than about 1 inch away from said fourth fluid twisting means;and

. said second fluid twisting means is from about 12 to about 500 inchesaway from said third fluid twisting means. The process of claim 4,wherein: said fibrillatable tape is maintained at a tension of about 0.1grams per denier, from about 40 to about 80 p.s.i.g. of air pressure aresupplied to said twisting means, and said second fluid twisting means isfrom about 15 to about 72 inches away from said third fluid twistingmeans.

1. A process for fibrillating a fibrillatable tape at a throughput speedof greater than 500 feet per minute comprising the steps of: a.subjecting a travelling fibrillatable tape to at least four fluidtwisting means; b. tensioning said travelling fibrillatable tape so thatit is under a tension of from about 0.05 to about 0.2 grams per denierwhile being subjected to said fluid twisting means; and c. contactingsaid tape with a vortex of whirling fluid in each of said twistingmeans, wherein said vortex of whirling fluid rotates around the axis oftravel of the tape and the direction of rotation of the vortices isopposite in adjacent twisting means, whereby the direction of twistimparted to the tape is completely reversed between adjacent twistingmeans.
 2. The process of claim 1, wherein: a. the first fluid twistingmeans said tape is subjected to is no further than 3 inches away fromthe second fluid twisting means said tape is subjected to, and the thirdfluid twisting means said tape is subjected to is no further than 3inches away from the fourth fluid twisting means said tape is subjectedto; and b. said second and third fluid twisting means are from about 6to about 1000 inches apart.
 3. The process of claim 2, wherein: a. thefluid supplied to said twisting means is air, b. from about 10 to about250 p.s.i.g. of air pressure are supplied to each of said twistingmeans, whereby, the velocity of said air in said twisting means is fromabout 0.5 to about 1.0 sonic velocity, and c. said fibrillatable tape iscomprised of at least 90 percent (by weight) of poly(ethyleneterephthalate)
 4. The process of claim 3, wherein: a. said fibrillatabletape is maintained at a tension of from about 0.05 to about 0.15 gramsper denier; b. from about 20 to about 100 p.s.i.g. of air pressure aresupplied to each of said twisting meaNs; c. said first fluid twistingmeans is no further than about 1 inch away from said second fluidtwisting means, and said third fluid twisting means is no further thanabout 1 inch away from said fourth fluid twisting means; and d. saidsecond fluid twisting means is from about 12 to about 500 inches awayfrom said third fluid twisting means.
 5. The process of claim 4,wherein: a. said fibrillatable tape is maintained at a tension of about0.1 grams per denier, b. from about 40 to about 80 p.s.i.g. of airpressure are supplied to said twisting means, and c. said second fluidtwisting means is from about 15 to about 72 inches away from said thirdfluid twisting means.